In 97 human cadavers the valves of the following blood vessels were investigated with regard to their cusps and their sizes and positions: the internal jugular veins, the subclavian veins, the brachiocephalic veins, and the superior vena cava. The cusps of each of the valves, which consist of two or three parts, are neither always of equal size nor obligatorily sufficient. Unipartite valves may be sufficient as well as insufficient. Internal jugular veins: The inferior bulb of the internal jugular vein is provided with valves which in 6 of the cases consist of three parts, in 66 of two parts, and in 15 of only one cusp. The concave margins of most of them go down as far as the venous angle. The convex edges attached to the wall of the vein extend to a higher level on the right side than on the left. In 13 there do not exist any valves. Varieties are described separately in this paper.Subclavian veins: Valves are found along the length of the vessel. Only few of them reach the venous angle. In rare cases there exist two valves: one at the beginning, the other at the end of the subclavian vein. In 4 of the cases the valves consist of three, in 75 of two cusps. In 12 they are unipartite. In 9 there are no valves to be found. The right side is more often without valves than the left. Brachiocephalic veins: Only a minority of these vessels is provided with valves. Most of these consist of one cusp, are insufficient, and are situated in the left innominate vein. In the right brachiocephalic vein, which is generally supposed to be valveless, there were found two valves which seemed to replace those of the bulb. Superior vena cava: In only 1 case a valve – unipartite and insufficient – was found in the superior vena cava close to its opening into the right atr
展开▼
